Rare are the chateaux that have been reduced to nothing and brought back to life with the wave of a magic wand. Such, however, is the story of Pierrefonds, in the Oise region, which was born twice. Equipped with the latest advances in military technology, the original chateau (c. 1400) was also an elegant palace, the residence of the man who had it built : the powerful Louis d'Orléans, duke of Valois and brother of Charles VI, the mad king. Constructed during a respite in the Hundred Years War, the redoubtable fortress came through the civil war between the Armagnacs and the Burgundians pretty well. It was a different matter altogether during the follies of the Wars of Religion and the ravages of the Leaguers. Infuriated, Cardinal Richelieu laid siege to Pierrefonds, demolishing the citadel so that it could no longer be put to military use. For two-anda-half centuries, the majestic ruins languished in obscurity. Helped on by Romanticism and the growing awareness of cultural heritage, Napoleon III, the writer Prosper Mérimée, and Eugène Viollet-le-Duc - an out-standing architect - all agreed that Pierrefonds must not be left to perish. The forlorn stones were given a new lease on life : the exteriors were rebuilt almost exactly as they were, but the interiors very much bear the mark of Viollet-le-Duc. After works lasting a quarter of a century, the chateau became a museum of military architecture and not an imperial residence. The early existence of the chateau is largely unknown, as are its tribulations and destruction. The restoration of Pierrefonds was an undertaking whose scope, materials, innovations, and decorative daring were barely imaginable. This book recounts the double saga of this historical monument, which is certainly worth a pilgrimage. It is also one of the most spectacular of Viollet-le-Duc's countless "salvage operations" and building projects.